place your secret message here, but it WILL
print out.
This part of Missouri is known for its caves, springs, and rock
formations. One of the common rocks you will find is the quartz
geode.
All along this natural sandstone and limestone wall you will
find geodes all over the walls. Take the time to look and explore
this neat little trail ocated in Hannibal, MO.
Geodes are usually a hollow mass which contain minerals such as
quartz. They are formed by water that has become trapped in a rock
or in crevices of rocks. Missouri geodes vary in size and can be
found anywhere from fields to caves and mines. They are really
common in several locations in northeast Missouri.
Geodes have no values or use other than for ornamental purposes.
The only way to positively identify that a round rock is a geode,
is to break or cut it in half and view its contents.
The geology of Geodes
Geodes are geological rock formations which occur in sedimentary
and certain volcanic rocks. Geodes are essentially rock cavities or
vugs with internal crystal formations or concentric banding. The
exterior of the most common geodes is generally limestone or a
related rock, while the interior contains quartz crystals and/or
chalcedony deposits. Other geodes are completely filled with
crystal, being solid all the way through. These types of geodes are
called nodules.
Geodes can form in any cavity, but the term is usually reserved
for more or less rounded formations in igneous and sedimentary
rocks, while the more general term '"vug"' is applied to cavities
in fissures and veins. They can form in gas bubbles in igneous
rocks, such as vesicles in basaltic lavas, or as in the American
Midwest, rounded cavities in sedimentary formations. After rock
around the cavity hardens, dissolved silicates and carbonates are
deposited on the inside surface. Over time, this slow feed of
mineral constituents from groundwater or hydrothermal solutions
allows crystals to form inside the hollow chamber. Bedrock
containing geodes eventually weathers and decomposes, leaving them
present at the surface if they are composed of resistant material
such as quartz.
Most geodes contain clear quartz crystals, while others have
purple amethyst crystals. Still others can have agate, chalcedony,
or jasper banding or crystals such as calcite, dolomite, celestite,
etc. There is no easy way of telling what the inside of a geode
holds until it is cut open or broken apart. However, geodes from
any one locality usually have a more restricted variety of interior
mineralization.
Geodes and geode slices are sometimes dyed with artificial
colors. Samples of geodes with unusual colors or highly unlikely
formations have usually been synthetically altered.
Geodes are common in this part of Missouri. They also are common
in Illinois, Indiana, Ohio and Kentucky.
NOTE! This EarthCache can be done from the listed coordinates.
No need to climb up on the cliff walls.
Have fun and take only
memories just like Cav Scout and the Echo the nosey
puppy.
(THE PHOTO IS OPTIONAL)
place your secret message here, but it WILL
print out.
To get credit for this EC, post a photo (optional) of you with
crystal geode in the background and please answer the following
questions.
1. What are the average sizes of some of the geodes you will
see?
2. What creates a geode?
3. Post a photo of a geode from the EarthCache site on the
day of your visit.
4. This question has been removed at the request of
groundspeak and nearby cache owner out of respect and integrity for
the location of their hide.
Email me the answers to the
questions through my geocaching profile.
Do not log this EC unless
you have answered the questions correctly. Failure to answer
questions or posting of answers in log entry may result in a log
deletion without notice.
Sources of information for the EarthCache taken from the
Missouri Department of Geology. We enjoy Earth Caches and want
people to get out and see what we see every time we go and explore
this great place called Earth.